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The start of the war is generally held to be September 1 1939, with the German invasion of Poland and subsequent declarations of war on Germany[4] by most of the countries in the British Empire and Commonwealth, and by France.[5][6] Many countries were already at war before this date, as a result of other events, and many who were not initially involved joined the war later.

Includes CC-BY-SA content from Wikipedia's World_War_II article (authors)
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